Lesions of the vitreoretinal juncture (VRJ) occur in both the posterior and peripheral fundus, either as spontaneous processes or as sequelae to known ocular or systemic diseases (including surgical procedures). In the posterior fundus the spectrum includes many proliferative lesions: simple epiretinal membranes (usually subtle and asymptomatic), surface wrinkling retinopathy (which may be accompanied by significant visual loss), and more complex nonvascular or vascular proliferations of the vitreoretinal juncture (which may culminate in irreversible tractional retinal detachments). In the peripheral fundus degenerative lesions (primarily tractional) are the major cause of retinal detachment. The proposed project will study in man the ultrastructural features of those factors which predispose the VRJ to degenerative or proliferative lesions, and in experimental animals similar factors under controlled laboratory conditions. With much of the background anatomical and simpler pathological conditions now clarified, the investigation will progress to the more complex nonvascular as well as vascular proliferative lesions (such as diabetic retinopathy) of the VRJ. Another no-less-important goal is an understanding of the degenerative lesions of the vitreoretinal juncture in the peripheral fundus, not only as they relate to rhegmatogenous retinal detachment, but also to proliferative lesions of the VRJ in the posterior fundus. It is expected that information from this project will provide a better understanding of lesions of the VRJ and thereby, improved prophylactic and therapeutic management of patients.